This invention relates generally to surgical tools and to systems for holding the bur therein. Much surgery today uses power drills and other tools. Because the tools must be small and portable for use in the operating room, the large forces associated with power tools are developed over small areas creating many design problems. One such problem concerns mounting a bur on the surgical tool and securing it for rotation in view of the high torque that may be developed.
Some surgical drills use a threaded chuck. Rotating the chuck urges members against the bur. Although such an arrangement is simple, it creates problems. Hand tightening of the chuck is usually insufficient because of the high torque developed by the tool. The chuck must be of a relatively small diameter in order to not restrict viewing the work area or interfere with surrounding tissue, but smaller chucks make manual tightening ineffective. A wrench or other tool is usually required for tightening and loosening the chucks. Wrenches can be misplaced easily, and misplacing a wrench prevents use of the drill. Also, it is time consuming to use a wrench.
Automatic chucks have been proposed. For example Lieb, U.S. Pat. No. 3,631,597 (1972) teaches a collet locking arrangement which is driven forward by members moving in a helical slot. The linkage is somewhat complicated and adds to the bulk of the tool.
It is an object of the present invention to provide an automatic chuck for a surgical tool which is locked upon initiation of the rotary motor. A further object of the present invention is to use the air which drives the pneumatic rotor motor to lock the bur in the drill. Another object is to provide a gripping system for the tool which holds the bur securely in the tool and yet will not jam locked. Still another object of the invention is providing a mechanism to jerk the grippers holding the bur loose to overcome any static friction that may have built up in the tool. It should be recognized that although the discussion herein is primarily concerned with surgical tools, the automatic chuck is applicable to any tool using a rotating member such as a drill or bore. Other objects will become evident in the discussion of the invention, and it will be shown how they and the aforesaid objects are met.